The coefficients \(A_i\)  are obtained numerically (see Table REF ) from the nonrelativistic Schrödinger three-body equation using the Hellman-Feynman theorem [1]}. As is seen from the Table the properly normalized coefficients correspond to the molecular spectroscopy picture: a rotational transition is proportional to \(1/\mu \)  and vibrational transition to \(\sqrt{1/\mu }\) . Only in the case of the \((3,0)\!\rightarrow \!(3,9)\)  transition, the coefficient becomes smaller than 0.5 since the upper state is already in that part of the potential well where anharmonicity is important.
